1. Field of Invention
The present invention belongs to the field of microelectronics technologies, and relates to a low-power consumption phase-change storage unit and a method for preparing the same, and specifically to a phase-change storage unit containing a TiSiN material layer and a method for preparing the same.
2. Description of Related Arts
The phase-change memory technology is established based on the concept that a phase-change film is applicable to a phase-change storage medium proposed by Ovshinsky during the late 60s (Phys. Rev. Lett., 21, 1450˜1453, 1968) and early 70s (Appl. Phys. Lett., 18, 254˜257, 1971) in the 20th century and provides an inexpensive storage device with stable performance. A phase-change memory is capable of being fabricated on a silicon chip substrate, and the research focuses on the key materials such as recordable phase-change films, heating electrode materials, thermal insulation materials and lead-out electrode materials are carried out about the device techniques: the physical mechanism researches of devices including how to reduce device materials. The basic principle of the phase-change memory is to apply an electrical pulse signal on a device unit to cause reversible phase changes between an amorphous state and a polycrystalline state for a phase-change material, and by means of distinguishing the high resistance in the amorphous state and the low resistance in the polycrystalline state, the operations of writing, erasing and reading information are implemented.
As a phase-change memory has the advantages such as high-speed read, large number of erasable times, being nonvolatile, small component size, low power consumption, resistance to strong vibrations and resistance to radiations, the International Semiconductor Industry Association believes that the phase-change memory is the device that is most likely to become the mainstream memory products in the future in place of the current flash memory and is the earliest to become commercially available products.
The read, write, erase operations on a phase-change memory are to apply, on a device unit, voltage or current pulse signals with different widths and heights: an erase operation (RESET), in which a short and strong pulse signal is applied to increase the temperature of the phase-change material in the device unit to a value above a melting temperature and fast cooling is then performed to implement the conversion of the phase-change material from a polycrystalline state into an amorphous state, namely, the conversion from state “1” into state “0”; an write operation (SET), in which a long and middle-strength pulse signal is applied to increase the temperature of the phase-change material to a value below the melting temperature and above the crystallization temperature, the temperature is kept for a period of time to urge the crystal nucleus to grow so as to implement the conversion from the amorphous state into the polycrystalline state, namely, the conversion from state “0” to state “1”; and a read operation, in which a very weak pulse signal that does not influence the state of the phase-change material is applied, the state of a device unit is read by measuring the resistance value thereof.
A lot of work has been done to reduce the power consumption of a device, including the proposal of various improved structures such as an annular electrode (Ahn, S. J. et al., Highly reliable 50 nm contact cell technology for 256 Mb PRAM, Symposium on VLSI Technology, 2005. Page 98-99), or the phase-change material and the transversal electrode size of a heating electrode are controlled within one same nanometer range; for example, phase-change nanometer points whose growth diameter and height may be controlled at about 50 nm; for example, the phase-change material is filled with electrical insulation and thermal insulation materials or is directly made into an annular phase-change material structure; for example, through the extrusion of the thermal insulating layer, the size of a region where a phase change occurs is about in the range of 2 nm to 200 nm; or the phase-change material layer is directly made into a shape in which the two ends are wider than the middle portion, and the upper and lower electrodes and alloy may be corroded through corrosive liquids with different corrosion rates; nan scale phase-change storage units in a shape of an “inverted tower” may also be fabricated, and phase-change materials and electrode materials may be filled in the inverted tower in a cavity array; or a transversal device structure may be adopted, a phase-change material is deposited on the carbon nanotube, and the transversal diameter may be controlled at 100 nm; or a thermal insulating layer with the heating layer made of a material such as ZrO2, HfO2, Ta2O5, TiO2, or Ti may be added; the work has effectively reduced the power consumption of the operations of a device.
In the document “Phase change memory line concept for embedded memory applications” published by NXP-TSMC, a blade structure was mentioned, and also in a patent (METHOD FOR PREPARING NANOMETER HEATING ELECTRODE OF PHASE-CHANGE MEMORY) of Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, the preparation by using a micrometer/nanometer processing technology was mentioned, which has implemented the method for preparing small holes on the basis of using large nanometer heating electrodes. However, in these researches, a method for silicon implantation through an ion beam was not mentioned, in which a TiN electrode is made into TiSiN, and the thickness of the TiSiN material layer is controlled by controlling the implantation amount of silicon; by means of a high-resistance transition layer of TiSiN, the effective operation region of the phase-change material is close to the electrodes, and the effective operation region is reduced; at the same time of enhancing the heating efficiency, the operating current is reduced, and especially, the operating current during the conversion from a polycrystalline state into an amorphous state is reduced, thereby implementing the high-density 1D1R integration and reducing the power consumption of a device.
In view of this, it is necessary to design a new phase-change memory unit structure with a TiSiN material to implement the low power consumption, high density and high stability of a device.